JP7310266B2 - Curing method and curing system - Google Patents

Description

The present invention relates to curing methods and curing systems.

A photo-curing technique for curing a photo-curing resin by irradiating it with ultraviolet rays is widely known, and is widely used in various fields such as printing, coating, and bonding. In the field of photo-curing technology, in order to prevent discoloration such as yellowing of the base material due to ultraviolet rays, the base material is shielded by a mask or the like so that the ultraviolet light does not directly hit the base material, or light with a wavelength of 300 nm or less is selected. Techniques for cutting with a filter or the like have been proposed (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2010-230702

However, in the case of shielding with a mask, if the size of the coating range of the photocurable resin on the substrate increases or the shape of that range becomes complicated, the cost of the mask increases, and the portion where the substrate is exposed increases. However, there is a problem that the masking process of the method is troublesome.
In addition, when cutting light with a wavelength of 300 nm or less, most of the wavelength region of ultraviolet rays is cut, so there is a problem that the energy efficiency decreases and the curability deteriorates depending on the material of the photocurable resin. be.

An object of the present invention is to provide a curing method and a curing system capable of efficiently curing a photocurable resin while suppressing discoloration of a substrate at a low cost.

The present invention relates to a curing method in which an acrylic photocurable resin coated on the surface of a base material made of polyvinyl chloride or polycarbonate is cured by irradiating it with ultraviolet light from a discharge lamp, and the wavelength range is from 200 nm to 450 nm. When the integrated irradiance of is "1", the integrated irradiance ratio of the first wavelength region from a wavelength of 200 nm to a wavelength of 230 nm is "0.017" or less, and the second wavelength region from a wavelength of 230 nm to a wavelength of 300 nm The ultraviolet rays are irradiated so that the integrated irradiance ratio of is "0.15" or more.

The present invention is characterized in that, in the above-described curing method, the integrated irradiance ratio in the first wavelength range is 0.008 or less.

The present invention is characterized in that, in the above-described curing method, the integrated irradiance ratio in the first wavelength range is "0.001" or less.

According to the present invention, in the above curing method, the photocurable resin is a resin material containing a mixture of a photopolymerizable monomer and a photopolymerizable oligomer as a main component.

The present invention provides a light source device for curing an acrylic photocurable resin coated on the surface of a substrate made of polyvinyl chloride or polycarbonate by irradiating ultraviolet light from a discharge lamp, and the acrylic photocurable resin. and an optical filter for controlling the spectral characteristics of the irradiated ultraviolet rays, and the ultraviolet rays from the light source device are irradiated onto the acrylic photocurable resin through the optical filter, so that the wavelengths range from 200 nm to 450 nm. When the integrated irradiance of the region is set to "1", the integrated irradiance ratio of the first wavelength range from a wavelength of 200 nm to a wavelength of 230 nm is "0.017" or less, and the second wavelength from a wavelength of 230 nm to a wavelength of 300 nm. Provided is a curing system characterized in that the photocurable resin is irradiated with ultraviolet rays so that the integrated irradiance ratio of the area is "0.15" or more.

ADVANTAGE OF THE INVENTION According to this invention, a photocurable resin can be hardened|cured efficiently, suppressing discoloration of a base material at low cost.

It is a figure showing composition of a coating system concerning an embodiment of the present invention. FIG. 4 is a diagram showing spectral transmission characteristics of an optical filter; It is a figure which shows the experimental result regarding the discoloration of a base material, and the hardening state of photocurable resin. FIG. 10 is a diagram showing experimental results of investigating the relationship between the integrated amount of light and the change in color difference when an optical filter is used;

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing the configuration of a coating system 1 according to this embodiment.
The coating system 1 is a system that coats (for example, hard coats) the surface 2A of the substrate 2 with a photocurable resin 4 using photocuring technology, and as shown in FIG. 6, and an ultraviolet irradiation device 10 for irradiating the surface 2A of the base material 2 with ultraviolet rays.
The base material 2 is a resin material formed into an appropriate shape. Further, the surface 2A of the substrate 2 is pre-coated with a photocurable resin 4 in a predetermined coating range Q. As shown in FIG. An appropriate coating device can be used for coating the photocurable resin 4 .

The photocurable resin 4 is an arbitrary resin material that has a characteristic of absorbing the ultraviolet rays emitted by the ultraviolet irradiation device 10 and is used for coating using a photocuring technique. The photocurable resin 4 is a resin material containing a photopolymerizable monomer or a photopolymerizable oligomer as a main component and to which a polymerization initiator is added. UV absorbers and light stabilizers are also added as appropriate. An acrylic resin is preferably used for the photocurable resin 4 .

In FIG. 1, the light source device 22 is a device that irradiates the substrate 2 with ultraviolet rays inside the nitrogen purge box 20, and controls the light source 23 that emits the ultraviolet rays and the distribution of the ultraviolet rays that the substrate 2 is irradiated with. and a light distribution control optical system 24 for controlling the light distribution.
As the light source 23, a discharge lamp that emits light in the ultraviolet wavelength range that is absorbed by the photocurable resin 4 is used. A high-pressure mercury lamp, an excimer lamp, a xenon lamp, or the like is used as such a discharge lamp.
The light distribution control optical system 24 controls the light distribution so that the surface 2A of the base material 2 is irradiated with ultraviolet rays while suppressing the illuminance unevenness.

The optical filter 26 is an optical member that controls the spectral characteristics of ultraviolet rays emitted from the light source device 22 to the substrate 2 . In the present embodiment, the optical filter 26 controls the spectral characteristics of ultraviolet rays, thereby suppressing discoloration due to ultraviolet irradiation in areas other than the coating area Q of the base material 2, and ensuring the photocurable resin 4 in the coating area Q. hardening it. Control of spectral characteristics by the optical filter 26 will be described later.

In addition, in the coating system 1 shown in FIG. 1, each part may be accommodated in one housing and configured as one apparatus.

Next, control of spectral characteristics by the optical filter 26 will be described in detail.
The inventor discovered through experiments that by controlling the spectral distribution of the ultraviolet rays irradiated to the base material 2 by the light source device 22, it is possible to cure the photocurable resin 4 while suppressing the discoloration of the base material 2. This experiment is described below.

<Experiment>
In this experiment, the substrate 2 coated with the photocurable resin 4 was irradiated with ultraviolet rays from the light source device 22 through the optical filter 26, and the presence or absence of discoloration of the substrate 2 and the cured state of the photocurable resin 4 were examined. .
The light source 23 of the light source device 22 has a glass tube made of ordinary quartz and uses an 8 kW class high-pressure mercury lamp. was measured using
One type of high-pressure mercury lamp has an ozone-free glass tube. However, in the ozoneless tube high-pressure mercury lamp, as the temperature of the ozoneless tube increases, the spectral characteristics of the ultraviolet rays shift to shorter wavelengths, and the spectral characteristics of the ultraviolet rays with which the photocurable resin 4 is irradiated become unstable. For this reason, in this experiment, it was decided to use a high-pressure mercury lamp with an ordinary quartz glass tube, which has relatively stable spectral characteristics, instead of a high-pressure mercury lamp with an ozoneless tube.

Polyvinyl chloride (PVC) was used for the base material 2 .
For the discoloration of the substrate 2, the color difference was measured using a spectrophotometer (CM-700d manufactured by Konica Minolta, Inc.) on the surface 2A of the substrate 2 before and after UV irradiation. As a result of the measurement, a color difference value of 2 or more "ΔE ^* ab" was judged to be discolored.

As the photocurable resin 4, a paint (HH9986U-N7) manufactured by Fujikura Kasei Co., Ltd. was used as a sample mainly composed of a mixture of a photopolymerizable monomer and a photopolymerizable oligomer. Samples were prepared according to the recommended curing conditions for the paint. Specifically, the photocurable resin 4 was applied to the surface 2A of the substrate 2 in a film thickness of about 10 μm using a bar coater, and then pre-dried at 60° C. for 5 minutes.

The cured state of the photocurable resin 4 after irradiation with ultraviolet rays is evaluated by a finger, and when the surface of the photocurable resin 4 is not scratched, the cured state is evaluated as being good (that is, it is reliably cured). bottom.

As for the irradiation conditions of the ultraviolet rays from the light source device 22, the conditions were used in which the photocurable resin 4 of the sample is cured satisfactorily when the ultraviolet rays of the light source device 22 are not passed through the optical filter 26 and the sample is irradiated. Such irradiation conditions include the illuminance of ultraviolet rays, the separation distance between the light source device 22 and the sample, the transport speed of the sample (that is, the irradiation time), and the integrated amount of light. The integrated amount of light is a value obtained by accumulating the illuminance of the ultraviolet rays irradiated to the sample over the irradiation time.
The irradiation conditions used in this experiment were an illuminance of 300 mW/cm ² , a separation distance of 140 mm, a transport speed of 1.8 m/min, and an integrated amount of light of 1000 mJ/cm ² , and each sample was irradiated with ultraviolet light under these irradiation conditions. bottom.
Then, the optical filter 26 was placed between the light source device 22 and the sample, and the sample was irradiated with ultraviolet light under the same irradiation conditions to evaluate the discoloration and curing state when the optical filter 26 was used.

The optical filter 26 includes UV-25 (manufactured by Toshiba Glass Co., Ltd.), UV-29 (manufactured by Asahi Techno Glass Co., Ltd.), U330 (manufactured by HOYA Corporation), UVCF2024 (manufactured by Iwasaki Electric Co., Ltd.), and a borosilicate glass filter. (manufactured by Shin-Etsu Quartz Co., Ltd.), alkali-free glass filter (manufactured by Shin-Etsu Quartz Co., Ltd.), and ozoneless quartz M235 (manufactured by Shin-Etsu Quartz Co., Ltd.). These spectral transmission characteristics are shown in FIG.

FIG. 3 is a diagram showing experimental results.
In the figure, "accumulated irradiance" is a value obtained by simply accumulating irradiance in each wavelength range, and its unit is mW/cm ² .

As shown in the figure, when the optical filter 26 is not used, the photocurable resin 4 is in a good cured state, but the surface 2A of the substrate 2 is often yellowed.
On the other hand, it can be seen that the occurrence of yellowing is minimized regardless of which optical filter 26 is used. Since all of these optical filters 26 attenuate the first wavelength region A1 from the wavelength of 200 nm to the wavelength of 230 nm, the first wavelength region A1 has a relatively large influence on the discoloration of the substrate 2. It is presumed that the illuminance of the first wavelength region A1 is suppressed, thereby reducing discoloration.

Also, looking at the experimental results in FIG. 3, the integrated irradiance in the wavelength range from 200 nm to 450 nm (hereinafter referred to as the "standard UV wavelength range"), which is generally referred to as the wavelength range of ultraviolet rays, was set to "1". It can be seen that yellowing is reduced when the integrated irradiance ratio of the first wavelength region A1 is at least "0.017" or less. When the optical filter 26 is other than "M235", yellowing is reduced if the integrated irradiance ratio of the first wavelength band A1 is "0.008" or less. In particular, if the integrated irradiance ratio of the first wavelength band A1 is "0.001" or less, yellowing can be suppressed in any of the optical filters 26 shown in FIG.
The light in the first wavelength region A1 has higher light energy (E) than light in other wavelength regions in the standard ultraviolet wavelength region, and contributes to enhancing the curability of the photocurable resin 4 . Therefore, it is desirable that the integrated irradiance of the first wavelength region A1 is not "zero".

The inventor also conducted a comparative experiment in which a high-pressure mercury lamp in which an ordinary quartz glass tube was coated with an ozone-less coating was used as the light source 23 and ultraviolet rays were irradiated under the same irradiation conditions without using the optical filter 26 . In this comparative experiment, when the integrated irradiance in the standard ultraviolet wavelength range is set to "1", the measurement result that the integrated irradiance ratio in the first wavelength range A1 is "0.029" is obtained. Compared to the case of "no optical filter", the integrated irradiance ratio of the first wavelength band A1 was sufficiently small. However, even with such an integrated irradiance, there were many discolorations. Therefore, it is inferred that discoloration increases when the integrated irradiance ratio of the first wavelength region A1 is at least "0.029" or more.

The inventor conducted an experiment to investigate the relationship between the integrated amount of light and the change in color difference when the optical filter 26 was used. The results of this experiment are shown in FIG.
As shown in FIG. 4, in the absence of the optical filter 26, the color difference greatly increases with an increase in the integrated amount of light, and more yellowing occurs remarkably. On the other hand, when the optical filter 26 is used, the change in color difference is small with respect to the increase in the integrated illuminance, and yellowing can be sufficiently suppressed.

Next, looking at the results of the cured state of the photocurable resin 4 in FIG. It can be seen that not all the optical filters 26 are necessarily in a good cured state.
In the standard ultraviolet wavelength range, the light energy (E) is the second largest after the first wavelength range A1, and the wavelength range from 230 nm to 300 nm (hereinafter referred to as "second wavelength area A2"), when the integrated irradiance ratio of this second wavelength area A2 is "0.146" or more with respect to the standard ultraviolet wavelength area, the cured state is good, but "0. If it is less than 118", the cured state will not be good. Therefore, if the integrated irradiance ratio of the second wavelength region A2 is at least "0.146" or more, the cured state is assumed to be good, and if the integrated irradiance ratio is "0.15" or more, it is definitely good. It is presumed that a good cured state can be obtained.

Here, considering that the absorption wavelength region of the photopolymerization initiator mainly exists on the longer wavelength side than 300 nm, which is the upper limit of the second wavelength region A2, the cured state of the photocurable resin 4 is , it can be said that not only the action of the polymerization initiator but also the absorption action of the main component of the photocurable resin 4 in the second wavelength region A2 has a great influence.
By setting the integrated irradiance ratio of the second wavelength region A2 to 0.15 or more when irradiating ultraviolet rays, sufficient energy is given to the main component of the photocurable resin 4 to obtain a favorable cured state. , the photo-curing resin 4 can be efficiently cured as compared with the conventional technology that cuts light with a wavelength of 300 nm or less.

The inventors have conducted the same experiment by changing the resin material of the base material 2 to polycarbonate (PC), and have confirmed that the same results as those of polyvinyl chloride can be obtained with respect to the cured state and discoloration.
Furthermore, the inventor conducted an experiment in which the resin material of the base material 2 was changed to polyamide synthetic fiber resin, ABS resin, polypropylene (PP), and acrylic resin, and an experiment in which the material of the base material 2 was changed to paper. In all these experiments, many discolorations were confirmed even when the integrated irradiance ratio of the first wavelength region A1 was "0.017" or less.

From the above, the following matters are derived.
That is, the photocurable resin 4 coated on the surface 2A of the base material 2 made of polyvinyl chloride or polycarbonate is irradiated with ultraviolet rays emitted from a high-pressure mercury lamp of a common quartz glass tube without passing through the optical filter 26. Discoloration of the base material 2 can be suppressed by lowering the integrated irradiance of the first wavelength region A1 by controlling the spectral characteristics of the ultraviolet rays by the optical filter 26 with respect to the integrated amount of light when the photocurable resin 4 is cured.
Further, with respect to the irradiation conditions, the optical filter 26 controls the spectral characteristics of the ultraviolet rays so that the cumulative irradiance of the second wavelength region A2 is not excessively lowered, thereby improving the photocurable resin 4. can be cured.
In particular, when the integrated irradiance of the standard ultraviolet wavelength range is set to "1", the integrated irradiance ratio of the first wavelength range A1 is "0.017" or less, and the integrated radiation of the second wavelength range A2 When the illuminance ratio is "0.15" or more, discoloration of the base material 2 can be reliably suppressed, and the photocurable resin 4 can be reliably cured.

Comparing the spectral transmission characteristics of each optical filter 26 shown in FIG. It can be seen that the maintenance of the integrated irradiance of the two wavelength regions A2 can be most effectively achieved.

In the coating system 1 described above, the spectral characteristics of ultraviolet rays are controlled by the optical filter 26, so that the integrated irradiance in the first wavelength region A1 and the integrated irradiance in the second wavelength region A2 change the color of the substrate 2. is reliably suppressed, and the photocurable resin 4 is maintained at a value that can be reliably cured.
As a result, discoloration of the base material 2 due to ultraviolet irradiation can be suppressed without providing a mask on the surface 2A of the base material 2, and the photocurable resin 4 can be cured efficiently and reliably.

According to this embodiment, the following effects are obtained.

According to this embodiment, when the photocurable resin 4 coated on the surface of the substrate 2 made of polyvinyl chloride or polycarbonate is irradiated with ultraviolet rays emitted from the light source device 22 to be cured, the wavelength is from 200 nm. When the integrated irradiance in the standard ultraviolet wavelength range with a wavelength of 450 nm is "1", the integrated irradiance ratio in the first wavelength range A1 from a wavelength of 200 nm to a wavelength of 230 nm is "0.017" or less, and a wavelength of 230 nm. Ultraviolet rays were irradiated so that the integrated irradiance ratio of the second wavelength region A2 with a wavelength of 300 nm was "0.15" or more.
As a result, the discoloration of the base material 2 can be reliably suppressed, and the photocurable resin 4 can be reliably cured. Therefore, since it is not necessary to provide a mask on the surface 2A of the substrate 2 when irradiating the ultraviolet rays, the cost can be suppressed. In addition, by irradiating the photocurable resin 4 with the light of the second wavelength region A2, the photocurable resin 4 can be efficiently cured as compared with the conventional technology that cuts off wavelengths of 300 nm or less.

The above-described embodiment is merely an example of one aspect of the present invention, and modifications and applications are possible without departing from the gist of the present invention.

In the above-described embodiment, the coating system 1 was exemplified as a curing system for curing the photocurable resin 4, but the present invention is not limited to this, and an appropriate system for coating and curing the photocurable resin 4 on the surface 2A of the base material 2 may be used. The present invention can be applied to curing systems.

In the above-described embodiments, unless otherwise specified, various numerical values do not intentionally exclude ranges around these numerical values, as long as they have the same effect or critical significance , includes the surrounding range (so-called equivalent range).

1 Coating system (curing system)
2 base material 4 photocurable resin 10 ultraviolet irradiation device 20 nitrogen purge box 22 light source device 23 light source (discharge lamp)
26 optical filter A1 first wavelength region A2 second wavelength region Q coating range

Claims (4)

In a curing method in which an acrylic photocurable resin coated on the surface of a base material made of polyvinyl chloride or polycarbonate is cured by irradiating ultraviolet light from a discharge lamp,
When the integrated irradiance in the wavelength range from 200 nm to 450 nm is "1", the integrated irradiance ratio in the first wavelength range from 200 nm to 230 nm is "0.017" or less, and the wavelength is 230 nm. A curing method characterized by irradiating the ultraviolet rays so that the integrated irradiance ratio of the second wavelength region from 300 nm to 300 nm is "0.15" or more. 2. The curing method according to claim 1, wherein the integrated irradiance ratio of said first wavelength band is "0.008" or less. 3. The curing method according to claim 1, wherein the integrated irradiance ratio of the first wavelength band is "0.001" or less. 4. The curing method according to any one of claims 1 to 3, wherein the photocurable resin is a resin material mainly composed of a mixture of a photopolymerizable monomer and a photopolymerizable oligomer.

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